[Qt-creator] C++11 in Creator's source: Update required features

[Daniel Teske]

> Now, we need to discuss our coding guidelines regarding those new features.
> While we don't need a coding guideline for each C++ feature, I think for
> those new features it's worth having a guideline on when to use them and
> how to use them.
> 
> If anyone wants to propose a coding style, please come forward.

We had some discussions on some features in the office, and based on that I'd 
like to propose the following coding guidelines:

- Use Delegating constructors, Initializer lists, Defaulted functions, Alias 
templates where it makes sense.  

Note: typedefs instead of Alias templates are still fine and there's no need to 
mass convert typedefs.

- You can use Scoped Enums.

Note: Scoped Enums seem to be a somewhat mixed bad, making them not strictly 
better than unscoped Enums. They are neither forbidden nor recommended. We 
probably need more experience with this.

- You can use nullptr, but 
Note: There was no consensus to ban nor to recommend them, but the majority 
didn't think nullptr brings a benefit, so individually maintainers might object 
to usage of nullptr.

daniel